Stabilized apparatus for drilling curved bores deviating from existing vertical wellbores



Sept. 8, 1953 zUBLlN 2,651,499

STABILIZED APPARATUS FOR DRILLING CURVED BORES DEVIATING FROM EXISTING VERTICAL WELL BORES Filed July 18, 1951 2 Sheets-Sheet l ATTORNEYS Sept. 8, 1953 J. A.-ZUBLIN 2,651,499

STABILIZED APPARATUS FOR DRILLING CURVED BORES DEVIATING FROM EXISTING VERTICAL WELL BORES 1951 7 Filed July 18 2 Sheets-Sheet 2 INVENTOR ATTORNEYS Patented Sept. 8, 1953 STABILIZED APPARATUS FOR'DRILLING CURVED BORES DEVIATING FROM EX- ISTING VERTICAL WELL BORES John A. Zublin, Los Angeles, Calif.

Application July 18, 1951, Serial N 0. 237,406

4 Claims.

This invention relates to improved, stabilized apparatus for drilling curved bores deviating from existing vertical well bores and has for its object the provision of apparatus embodying means forstabilizing thesame against unwanted and objectionable deformation when in use.

The drilling of curved bores into the producing formations of oil Wells extending thereinto from the existing vertical well bore and apparatus for effecting the drilling of a such deviating bores have been the subject matter of a number of prior 'patents issued to me and of applications filed by me,

One advantageous form of apparatus for use in the drilling of curved bores deviating from existing vertical well bores embraces a helically dovetail slotted, normally curved, flexible, resilient drill guide, a'flexible, nonresilient, sectional, Inetallic, tubular drive member extending through and rotatable within the-helically slotted, normally curved, flexible, resilient drill guide, the said flexible nonresilient drive member projecting upwardly from the normally curved drill guide for a distance adequate to insure the drill- .ing.of a curved boreof the desired length. The

flexible nonresilient drive member is connected at its upper end to a substantially rigid, tubular drill string that extends to the top of the well to be driven by the usual rotary drilling mechanism. The flexible nonresilient drive member carries for rotation therewith a drill bit at its lower or free end.

.In .the operation of the deviating bore drilling "apparatus just above briefly described, there is :toften a substantial length that is from 40 to 80 :feet or more of nonresilient flexible, sectional, metallic drill pipe disposed above the normally curved, helically slotted, resilient, flexible drill guide at the time drilling of a deviating bore from the existing well bore is initiated. It has been found that'when the drilling of a deviatingbore is initiated through the employment of such apparatus andexcessive-weight, due to inadvertence .orotherwise, is imposed on the drill stringat the surface of the Well, there is a tendency for the flexible nonresilient drill pipe sections of the .gdlilVe' member to buckle in the-vertical well bore :above the normally curved, flexible, helically slotted, resilient drill guit e. When such buckling of theflexible nonresilient drive member occurs, the elbow produced by the joints thereof is brought into contact with the wall of the vertical bore and, as the drill pipe is rotated, digs into the formation, forming what has come to be known as-a; key-seated cutout. Whenthe keyon the drill string the worse the situation becomes and will sometimes result in breaking the "flexible driving member which, because of its hardened surface and peculiar position, is very diflicult to fish from the well.

It is the specific purpose and object of the presentinvention to obviate the objections and difficulties hereinbefore recited by embodyinga-stabilizing element in the drilling apparatus. -Further and more specific purposes and objectsof the invention will become apparent as the description proceeds which will be made by reference to the accompanying drawings forming apart hereof and wherein Figure 1 is a view in side elevation of the drilling apparatus of the invention showing the'position of the same in an existing vertical well bore ready to initiate the. drilling of a curved, deviating bore.

Figure 2 is a fragmentary, detailed view disclosing the relationship of parts of the apparatus after the drilling of the curved bore has been initiated,

Figure 3 isa detailed View, partly in section, illustrating the relation of the stabilizer member to the-associated elements of the apparatus, and

Figure 4 is a view similar to Figure 2 disclosing asectional-stabilizer construction applicable .to the drilling of long, curved, deviating bores.

Referring to Figure l, a conventional rotary .drill table is diagrammatically illustrated at it) and the normally rigid drill string section II extends downwardly from the surface of the well. It will be understood that the drill string H' is of conventional form made up of sections of steel pipe and may well be several thousands of "feet in length. The lower section of the tubular drill string I l may suitably be provided with an annular enlargement I2 (see Figure 3). The upper end of the flexible nonresilient drill string drive member indicated generally at i3 is adapted tolbe threadedly connected, to the annular enlargement 12 of the rigid drill string l asindicated at I4 in Figure 3. The flexible nonresilient drive member is preferably constructed in accordance with the teachings of my Patent 2,5l5,366 and is made up of the individual sections 15 having the intermeshing dovetailed teeth 16. It will be appreciated that where a very long deviating bore is desired the flexible nonresilient drive member l3 may be made up of a plurality of sectional units much the same as the normally rigid, tubular drill string is made up. Such sections are adaptedto' be interconnected by threaded joints such as indicated at I1 (Figure 3). The lowermost portion of the flexible nonresilient drive member I3 projects downwardly through and is rotatable within the normally curved, flexible, resilient, drill guide [8, the bit l9 being carried at the extreme lower end of the flexible nonresilient drive member I3 and is mounted for rotation therewith. Thus, when the normally rigid drill string II and the flexible nonresilient drive member I3 are rotated from the rotary table II! at the surface of the well the bit I9 will be positively driven. The normally curved, flexible, resilient, helically slotted drill guide I8 is preferably constructed pursuant to the teachings of my United States Patent 2,515,365, there being provided intermeshing dovetailed teeth 20 along the helical slot of this drill guide.

The drill guide I8 may desirably have a ourvature in completely unstressed configuration of a radius of about 16 feet with the pitch of the spiral being about nine inches for a four and one-half inch diameter drill pipe. The drill guide I8 is adapted to be forcibly flexed to less than its normal curvature to permit of its introduction into the vertical well bore indicated at 2|, the forcible flexing of the drill guide I8 to this lesser curvature being adequate to store suflicient potential energy therein to force the guide and the rotating drill bit I9 from the existing bore in the desired oriented direction, similar to the method set forth in some detail in my United States Patent 2,336,338.

While the equipment thus far described in this specification is highly effective for the drilling of curved bores deviating from existin vertical well bores in many types of formation, caution must be employed in the handling of the apparatus so as to avoid imposition of too great weight on the drill bit. In the practical operation of rotary drilling equipment, however, oftentimes through inadvertence, miscalculation or otherwise, greater weight is imposed on the drill bit than can be accommodated by previously described apparatus with the result that the flexible nonresilient drive member I3 is caused to buckle at one or more of its joints formed by the intermeshing dovetailed teeth I6. Such buckling creates a rather sharp angle with the hardened edges of the adjacent sections constituting real cutting or shearing instrumentalities which bite into and cut out a V-shaped groove in the formation which tends to lock the apparatus against further downward movement and presents so much friction to the rotation of the apparatus as to sometimes result in the severance thereof through twisting off or breakin of some of the intermeshing dovetailed teeth I6 of the flexible drive member I3. To obviate this buckling action I have, pursuant to the present invention, encased the flexible nonresilient drive member for that portion thereof which projects above the normally curved resilient drill guide I8 with a stabilizer tube 22, the lower end of which may desirably be helically slotted as indicated at 23 to give adequate flexibility thereto to permit the same to assume the necessary position in the vertical bore to facilitate the free movement of the remaining portions of the apparatus into the deviating bore. The upper end of the encasing stabilizer tube 22 is preferably swaged or otherwise formed with an opening 24 of considerably smaller diameter than the inside diameter of the main portion of the stabilizer tube 22 to thus provide the annular shoulder 25 which is adapted to engage the upper face of the enlarged portion I2 at the lower end of the normally rigid, tubular drill string II. It will be understood that the drill string l I is free to move downwardly through the opening 24 in the stabilizing tubular member 22. When, however, the drill string II is drawn upwardly the enlarged portion I2 engages the shoulder 25 and the tubular stabilizer member 22 will be drawn upwardly with the apparatus.

It will be noted that the exterior diameter of tubular stabilizer member 22 is substantially greater than the exterior diameter of the normally curved, resilient drill guide I8 as more particularly indicated at the lower end 26 of the tubular stabilizer member 22. The arrangement is such that when the bit [9 and the normally curved, resilient drill guide I8 have passed into a deviating bore such as 21 (Figure 2) the shoulder 26 of the tubular stabilizer member 22is adapted to lodge against the formation at the point of juncture of the deviating curved bore 21 with the vertical bore 2I. Because the curved bore 2'1 is of less diameter than the exterior diameter of the tubular stabilizer member 22, the latter will not pass into the curved deviating bore 2'! but will be held in the position substantially shown in Figure 2. The normally rigid, tubular drill string I I will pass down through the opening 24 and the flexible nonresilient drive member I3 will be fed downwardly through the tubular stabilizer member 22, the curved lower end of which may assume substantially the configuration shown in Figure 2, allowing the flexible nonresilient drive member I3 to advance into the curved bore while the lower end thereof rotates within the normally curved, flexible, resilient drill guide IS. The tubular stabilizer member 22 functions to prevent unwanted buckling of the flexible drive member I3 and maintains the latter in substantially straight form in the vertical bore while facilitating ease of rotation thereof.

If desired, antifriction means may be interposed between the tubular stabilizer member 22 and the flexible drive member I3 to further facilitate ease of rotation thereof.

Inasmuch as the curved bore 21 is of much less diameter than the vertical bore 21 of the existing well, no objectionable buckling of the flexible nonresilient drive member I3 can occur in the curved bore since the walls of the latter serve in and of themselves to stabilize the flexible drive member.

If desired, the tubular stabilizer member 22 may be made up of several sections interconnected as indicated at 21 in Figure 3. In Figure 4 the stabilizer member 22 is illustrated as made up of a series of interconnected sections only the lower one of which is provided with a helical slot 23 to give the necessary flexibility thereto. An enlarged stop ring 28 which may take the form of a pipe coupling is desirably positioned in the drill string II a distance above the annular enlargement I2 approximately equal to the over-all length of the flexible drive member I3. The stop ring 28 thus functions to limit upward movement of the tubular stabilizer member 22. Normally, the weight of the tubular stabilizer member 22 will be adequate to keep the same in its lowermost position during insertion of the apparatus into a well bore, that is, with the shoulder 25 in engagement with the enlarged portion 12. If, for any reason such as contact with the Wall of a crooked well bore, the tubular stabilizer member 22 is temporarily pulled upwardly on the drill string II its upward movement will be limited by the stop ring 28 and as soon as the frictional contact with any irregularity in the vertical bore has been passed, the weight of the member 22 will again return it to its normal position with the shoulder 25 in engagement with the enlarged portion l 2. In this way it is possible to stabilize a very substantial length of flexible nonresilient drive section of the apparatus against undesired buckling under all conditions of operation.

Having thus described my invention, what I claim is:

1. An apparatus for drilling curved deviating bores from existing vertical well bores comprising a combination unit adapted to be suspended from the lower end of a conventional rotary drill string, said unit embracing a flexible sectional metallic tubular nonresilient drive member, means for connecting the upper end of said drive member to the lower end of a rotary drill string to rotate in unison therewith, a drill bit carried at the lower end of said drive member for rotation thereby, a normally curved flexible resilient helically slotted metallic tubular drill guide surrounding a substantial portion of said drive member extending immediately above said drill bit and a separate tubular stabilizer member surrounding a further portion of said drive member and extending for a substantial distance above said drill guide, said drill guide being free to advance with said bit upon projection of said drive member through said stabilizer member.

2. An apparatus for drilling curved deviating bores from existing vertical well bores comprising a combination unit adapted to be suspended from the lower end of a conventional rotary drill string, said unit embracing a flexible sectional metallic tubular nonresilient drive member, means for conneotingthe upper end of said drive member to the lower end of a rotary drill string to rotate in unison therewith, a drill bit carried at the lower end of said drive member for rotation thereby, a normally curved flexible resilient helically slotted metallic tubular drill guide surrounding a substantial portion of said drive member extending immediately above said drill bit, a separate tubular stabilizer member surrounding a further portion of said drive member and extending for a substantial distance above said drill guide, the inner diameter of said tubular stabilizer member being larger than the exterior diameter of said drive member to permit free rotation and longitudinal movement of said drive member therein, the exterior diameter of said stabilizer member being greater than the exterior diameter of said drill guide to preclude entry of said stabilizer member into a curved deviating bore drilled by the apparatus, said drill guide being free to advance with said bit upon projection of said drive member through said stabilizer member.

3. An apparatus for drilling curved deviating bores from existing vertical well bores comprising a combination unit adapted to be suspended from the lower end of a conventional rotary drill string, said unit embracing a flexible sectional metallic tubular nonresilient drive member, means for connecting the upper end of said drive member to the lower end of a rotary drill string to rotate in unison therewith, a drill bit carried at the lower end of said drive member for rotation thereby, a normally curved flexible resilient helically slotted metallic tubular drill guide surrounding a substantial portion of said drive member extending immediately above said drill bit, a separate tubular stabilizer member having an upper relatively rigid section and a lower relatively flexible section surrounding a further portion of said drive member and extending for a substantial distance above said drill guide, the inner diameter of said tubular stabilizer member being larger than the exterior diameter of said drive member to permit free rotation and longitudinal movement of said drive member therein, the exterior diameter of said stabilizer member being greater than the exterior diameter of said drill guide to preclude entry of said stabilizer member into a curved deviating bore drilled by the apparatus, said drill guide being free to advance with said bit upon projection of said drive member through said stabilizer member.

4. An apparatus for drilling curved deviating bores from existing vertical well bores comprising a normally curved flexible resilient helically slotted drill guide, a flexible nonresilient tubular drive member rotatable within and extending a substantial distance above said normally curved resilient drill guide, a drill bit carried at the lower end of said flexible nonresilient tubular drive member, means for connecting the upper end of said flexible tubular drive member to the lower end of a substantially rigid rotatable drill string, a tubular stabilizer member surrounding a portion of the flexible nonresilient tubular drive member above said normally curved resilient drill guide, said tubular stabilizer member being constructed to permit projection of the flexible nonresilient drive member downwardly therethrough, the exterior diameter of said tubular stabilizer member being substantially greater than the exterior diameter of the said normally curved drill guide to provide a shoulder at the lower end of said tubular stabilizer member adapted to prevent entry of said stabilizer member into a curved deviating bore drilled by the apparatus, said drill guide being free to advance with said bit upon projection of said drive member through said stabilizer member.

JOHN A. ZUBLIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,296,161 I-Iall Sept. 15, 1942 2,336,338 Zublin Dec. 7, 1943 2,344,277 Zublin Mar. 14, 1944 2,515,365 Zublin July 18, 1950 2,515,366 Zublin July 18, 1950 

